In the process of aircraft approach and landing, stable and reliable long-range high-precision spatial angle measurement is one of the most critical technical challenges. The key issue lies in achieving accurate spatial angle measurement under various interference factors, including terrain complexity, meteorological conditions, and potential electronic interference. There has been significant research on long-range high-precision spatial angle measurement technologies for aircraft landing systems, such as instrument landing system (ILS) and microwave landing system (MLS), which perform well in open airspace without electromagnetic interference. However, in modern military applications, radio silence and radio frequency (RF) denial techniques have become common forms of electronic warfare. In such environments, the effectiveness of these systems is significantly reduced, or they may fail. To address these challenges, some scholars have explored vision-based spatial angle measurement technologies. However, vision-based systems are limited in their ability to provide large-scale, high-precision spatial angle measurements, and are also susceptible to interference from strong light and adverse weather conditions (such as haze and cloud cover), thus degrading their performance. In this paper, we propose a spatial angle measurement technique based on a laser time-grating field, offering a feasible solution for achieving remote and high-precision dynamic spatial angle measurement in radio silence and RF denial environments.

The spatial angle measurement technology based on the laser time-grating field is implemented through the collaboration of a reference station and a positioning unit. The reference station uses high-power lasers to emit two pulsed modulated laser beams containing time-grating encoded information. These laser beams are scanned uniformly in both the azimuth and elevation directions by two high-precision optical scanners. After being shaped by a precision optical system, the beams form two laser strips with specific geometric configurations. The laser strip scanned in the azimuth direction is referred to as the X-strip, and the one scanned in the elevation direction is referred to as the Y-strip. The scanning and encoding of these X and Y strips generate a two-dimensional laser time-grating field, forming the measurement space. Within the space, the positioning unit can determine its precise azimuth and elevation angles relative to the reference station by analyzing the time-grating encoded information, while considering the motion characteristics of the scanners. This enables high-precision two-dimensional spatial angle measurement.

In this paper, we propose a spatial angle measurement technology based on the laser time-grating field, where the reference station and the positioning unit collaborate to perform two-dimensional spatial angle measurements. A prototype system based on this technology is built, and static and dynamic angle measurement experiments are conducted in the field. The experimental results show that the static angle measurement error for the azimuth and elevation angles is -0.003359° and -0.001044°, respectively, while the root mean square errors for dynamic angle measurements are 0.001741° and 0.001739°, respectively. The positioning unit operates normally within a range of 6500 m from the reference station. With a scanning range of ±10° in both azimuth and elevation directions, the measurement space forms a conical region centered at the reference station. This demonstrates long-range, high-precision dynamic spatial angle measurement, fully validating the feasibility of this technology. While the operating range of this system is not as extensive as ILS and MLS, its accuracy in spatial angle measurement is far superior, particularly in radio silence and RF denial environments, which makes it an effective complement to current aircraft landing systems.

In this paper, we propose a spatial angle measurement technique based on the laser time-grating field. By establishing a precise relationship between the spatial scanning angle and the time reference, the high accuracy of time-based measurements is maximized. The spatial angle measurement accuracy achieved by this system surpasses that of ILS and MLS in environments with radio silence and RF denial. A prototype of the system has been constructed, demonstrating a working distance of at least 6 km and the angle measurement accuracy is 1?2 orders of magnitude greater than ILS and MLS. This provides a viable solution for achieving long-range, high-precision dynamic spatial angle measurement in radio silence and RF denial environments.